BEIJING – The violence that struck the Olympics on Saturday has cast a spotlight on China's security preparations in Beijing — and those preparations have been extensive.

The country is keeping millions of eyes peeled for threats to the 2008 Beijing Olympics games. Every inch of Beijing is being monitored by 300,000 security cameras with face-recognition technology. By contrast, only 8,000 electronic eyes were employed in Athens for the 2004 Summer Games.

China's unprecedented efforts weren't enough to prevent the attack Saturday by a Chinese man, who stabbed an American to death and injured another American, as well as a Chinese tour guide, before killing himself. The Americans were relatives of the coach of the U.S. men's volleyball team.

The U.S. Embassy is treating the violence as a tragic but isolated incident. Chinese government officials have remained tight-lipped about the attack.

Experts say threats are always present.

"The threat here is everything from terrorists to criminals to crazies," Ma Xin, a security expert and Olympic adviser, said in a FOX News interview that took place prior to the Saturday attack. "Our security is multilayered and we've had to think of every eventuality."

About 130,000 police and army officers are on guard in the Chinese capital, but larger still is a much less visible security force: the 300,000 volunteers watching for suspicious activity — and carefully eying foreigners.

Some critics have questioned whether China is employing too much security, including two anti-aircraft batteries near the main stadium and many more batteries ringing the city of Beijing.

Human rights groups say the threat of terrorism has been used to silence political dissidents and voices calling for democracy. Protesters who unfurl posters or political banners in Tiananmen Square are arrested and sent straight to jail.

The International Olympic Committee says the security measures are proportionate to the threat, and China is even allowing some countries to manage their own security.

"Most of the American team is not staying at the Olympic village but at a well-guarded university campus" in Beijing, said Xin.

American athletes also shied away from the Olympic village while competing in Athens in 2004, the first summer games after 9/11. Many of the athletes stayed on ships in Piraeus harbor, which allowed the American delegation more freedom for their guard force, as they weren't directly imposing on Greek territory.

In Beijing, Olympic planners made a compromise. "Here they're staying here and we're guarding their compound but we are allowing them to have their own security," said Xin.

Both America and China are worried about possible terrorist strikes on the games, and just a day before the opening ceremonies, a new threat emerged.

The Turkistan Islamic Party released an internet video Thursday threatening an attack on the Olympics. The group, which seeks independence in China's Xinjiang region and has launched attacks in the past, says Muslims should avoid trains, planes and buses in China.

China has engineered an effective lockdown on the city of 16 million, making it difficult to get food into Beijing. That has driven up the price of fruit and vegetables by about 100 percent, the price of meat by about 40 percent.

Many Chinese workers have been affected by factory shutdowns on the edge of the city, costing hundreds of millions as the government tries to improve air quality and imposes stringent controls on trucking.

China also refused to provide many visas in advance of the games, which it said was another needed security precaution.

"The problem is not that we have become too strict — the problem is before there were practically no restrictions or control at all," Xin said. "It was out of control — anyone could enter China and we had to bring this under reasonable control."